Rabbit Control ResearchCan learnings from possums be

applied to rabbits?

B. Warburton, G. Nugent, P. Fisher,J. Parkes, R. Clayton, G. Morriss

Outline

• Main research and operational aim

• What have we learnt from possums?

• Is there potential to apply this knowledge to rabbit control?

• Planned research projects

Current standard operational practice 2-3 kg/ha of 12g 1080 baits170-250 baits/ha for ≤ 20 possums & rats/ha

Why are we not using less?

Research and Operational Aim:To reduce sowing rates and cost

(a) Cereal pellet bait operations (n= 90)

0

4

8

12

16

20

1973-77 1978-82 1983-87 1988-1992 1993-97 1998-2002

Years

Mea

n so

win

g ra

te (k

g/ha

)

0

10

20

30

40

50

60

Cos

t ($/

ha)

(b) Carrot bait operations (n=51)

0

5

10

15

20

25

30

35

1973-77 1978-82 1983-87 1988-1992

1993-97 1998-2002

Years

Mea

n so

win

g ra

te (k

g/ha

)

0

10

20

30

40

50

Cos

t ($/

ha)

From Dave Morgan

What have we learnt?Prefeed…1

Cautious feeders Gluttons

< 1bait

0

12

24

36

48

60

72

84

1 2 3

Encounter

Bai

t ea

ten

(g)

>2 baits

0

12

24

36

48

60

72

84

1 2 3

Encounter

Bai

t ea

ten

(g)

Possum pen trials

What have we learnt?Prefeed…2

• Prefeed significantly increases the kill achieved

Possums

0%

50%

100%

0 1 2

N Pre feeds

% s

urv

iva

l (s

.e.)

Rats

0%

50%

100%

0 1 2

N Pre feeds

% s

urv

iva

l (s

.e.)

Results of field trial at Whirinaki (Nugent et al 2008)

Before pre-feeding During pre-feeding

Before pre-feeding During pre-feeding

5 days before prefeeding 5 days during prefeeding

What have we learnt?Prefeed…3

GPS location data from a possum before and during prefeed.

Prefeed line

What have we learnt?Bait aversion

3.00kg/ha broadcast

0

50

100

1 2 3 4 5 6 7 8 9Bait cluster #

% b

ait

ea

ten

Carrot Apple Cereal

Unpoisoned

0

50

100

1 2 3 4 5 6 7 8 9Bait cluster #

% b

ait

ea

ten

0% 50% 100%

Rata RdCereal

Te TehiCereal

Rata RdCarrot

Te TehiCarrot

% of baits

Gone Part eaten Untouched

After a carrot operation After a cereal operation

(b) After sowing

0

20

40

0.5 3.5 6.5 9.5 12.5

%

(a) Before sowing

0

20

40

0.5 3.5 6.5 9.5 12.5

%What have we learnt?

Bait fragmentation

Bait weight class (g)

Before sowing

0

10

20

30

0-1 2-3 4-5 6-7 8-9 10-1112-13 >14

% After sowing

0

10

20

30

40

0-1 2-3 4-5 6-7 8-9 10-1112-13 >14

%

No 7 bait RS5 bait

Bait weight class (g)

What have we learnt?Reducing the sowing rate…1

Sown at 3kg/ha

● ≤ 2g = sublethal● > 2g

What have we learnt?Reducing the sowing rate…2

Sown at 0.25kg/ha

What have we learnt?Reducing the sowing rate…3

Sown at 0.25kg/ha

100m

Potential to apply similar approach to rabbits…1

• Rabbit densities:

Common abundance index used is rabbits per spotlight kilometre (up to 300) Moller et al. 1999. Density estimates within patches up to 50 rabbits/ha

(mean 19/ha).

• Current bait sowing rates: 25 to 45kg/ha (up to 60kg/ha) At 30kg/ha and 5g baits applying 6000 baits/ha!

• Toxic loadings registered: Carrot = 0.02% (LD99 = c. 3mg/kg) – Need three 5-g baits Cereal = 0.04 & 0.06%

• For carrot bait at 0.02% 1080 and 50 rabbits/ha need atmost c. 150 baits (750g/ha).

Potential to apply similar approach to rabbits…2

0

10

20

30

40

50

60

70

<0.25 0.25 - 0.5 0.5 - 1.0 1.0 - 2.0 2.0 - 4.0 4.0 - 8.0 8.0 - 16.0

Perc

enta

ge

Weight class (g)

Carrot bait (Reliance cutter unscreened)Weight distribution

From Batchelor (1982)2007 ERMA 1080 reassessment:•All carrot bait for aerial application to be screened at a mean weight of 6g•Ground laying of bait does not have to be screened.

So what is the bait size 1080 conc distribution of sown bait?

Potential to apply similar approach to rabbits…3

0

5

10

15

20

25

30

35

1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008

Mea

n ra

bbit

s/km

Year

Secondary vs primary controlPrimary control (aerial 1080) needed after 8 years

Secondary control (helicopter shooting, night shooting, spot

poisoining)

From Lough 2009

• Can secondary control maintain the gains of RHD and remove the need for repeat primary control using 1080? – at what costs?

• How can conventional control and RHD be effectively integrated?

Planned Research…1• Project 1. A review paper: To re-assess the single dose

LD100 for 1080 and pindone.• Project 2. An analysis of bait size distributions and 1080

toxic loadings for cereal, screened carrot, and unscreened carrot before and after sowing.

• Project 3. Construct a probabilistic model of numbers of bait encounters needed to kill rabbits of different size and susceptibility – as done by Batchelor (1982) and Frampton et al. (1999).

• Project 4. An observational study of how rabbits react to carrot and cereal baits at first ever encounter, and test acceptance of a one-shot ‘perfect’ carrot bait with and without prefeeding.

Planned Research…2

• Project 5. Home range use and effect of prefeed on foraging patterns (GPS) – implications for trickle sowing.

• Project 6. Rabbits, coprophagy, and pindone. Can pindone be used as a one-hit application?

• Project 7. Secondary control – extending the benefits of RHD – what is effective and at what cost?

• Project 8. Integrating RHD with conventional control – development of a DSS for end-users.

• Project 9. Developing a web-based bibliography of all published and unpublished rabbit research literature:

- Jim Bell’s (MAF rabbit group)- Rabbit & Land Management Programme (special thanks to Don Ross for making MAF and RLMP material freely available)

From the late Jim Bell’s photo collection

A typical scientist!!